440 THE POPULAR SCIENCE MONTHLY. 



viewed in its light, the number of possible arrangements in the ovum 

 and spermatozoon grows into immensity. If we could imagine the head 

 of a spermatozoon as large as the Great Eastern, and the space repre- 

 sented by it filled with a wheel-work as fine as that of the smallest 

 lady's watch, our figure would still be far from giving any kind of a 

 representation of the ultimate division of matter. It is thus clear 

 that the head of a spermatozoon affords space and opportunity for the 

 endlessly numerous arrangements and various motions on which the 

 innumerable types and properties, with which this apparently so simple 

 organism is charged, finally depend. It may then, at all events, be 

 conceived that parental dyscrasies communicate themselves through 

 the blood to the germs in the testicles and ovaries. But now let a 

 group of ganglion-cells in the brain, if we may speak thus, be played 

 upon to a certain molecule-dance-figure. The blood can not be changed 

 by that. Consequently, the threads of the plexus spermaticus interims 

 must so work upon the semen-cells in the seminal canal, the egg-cells 

 in the after-growing Graafian pustules, that each act of exercise in the 

 course of growth leaves its mark on the egg or on the spermatozoon, 

 and that it is followed after years by the natural culmination of the 

 same molecule-dance-figure in the corresponding group of ganglion- 

 cells in the man or animal that has grown up out of that egg, or with 

 the aid of that spermatozoon. How the plexus spermatieus internus, 

 the connection of which with the brain is only of the loosest character, 

 brings this to pass, can not be found out. The conditions are no more 

 favorable for the comprehension of the kinds of exercise resting upon 

 nutritive and formative stimulation. 



As we have already pointed out, it appears that we might, in order 

 to verify the transmission of acquired properties, invoke the example 

 of hereditary diseases, from which our ancestors were in all probabil- 

 ity free, which chiefly visit more highly developed manhood, and the 

 transmission of which consequently resembles the transmission of ac- 

 quired properties. Still, we may question whether the first epileptic 

 attack, the first migraine, followed injuries which came upon a sound 

 adult, or whether the foundation for them was not laid in the egg or 

 the spermatozoon out of which the first sufferer grew. There re- 

 mains, for the confirmation of this view we will be honest the trans- 

 mission of acquired peculiarities, an hypothesis drawn solely from the 

 facts illustrating it, yet quite obscure in itself, which receives only 

 doubtful light through Darwin's "pangenesis." 



I believe now, gentlemen, that I have justified the expression with 

 which I introduced to you my intention to speak of exercise that is, 

 that it deserved a place in the scientific order of the day ; yet I need 

 not say explicitly how far I am from entertaining the thought that I 

 have contributed anything essential to the fulfillment of that object. I 

 consider that I have succeeded no further than more sharply to define 

 the eventual phylogenetic office of exercise and the direction of the 



